8th Grade Force and Motion
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. Forces can be added together only if they are
a. acting on the same object.
b. balanced forces.
c. unaffected by gravity.
d. substantial.
____
2. According to Newton’s third law of motion, when a hammer strikes and exerts force on a nail, the
nail
a. creates a friction with the hammer.
b. disappears into the wood.
c. exerts an equal and opposite force on the hammer.
d. moves at a constant speed.
____
3. Speed equals distance divided by
a. time.
b. velocity.
c. size.
d. motion.
____
4. When you know both the speed and direction of an object’s motion, you know the
a. average speed of the object.
b. instantaneous speed of the object.
c. distance the object has traveled.
d. velocity of the object.
____
5. The energy associated with motion is called
a. kinetic energy.
b. elastic potential energy.
c. gravitational potential energy.
d. nuclear energy.
____
6. The energy associated with the motion and position of an object is called
a. kinetic energy.
b. potential energy.
c. gravitational potential energy.
d. mechanical energy.
____
7. A car accelerates from rest to a speed of 24 m/s in 8 seconds. What is the car's average acceleration?
a. 16 m/s2
b. 24 m/s2
c. 3 m/s2
d. 192 m/s2
____
8. A student pushes a book across a table with a constant force. How would the acceleration of the
book change if the mass was doubled but the force was held constant?
a. The acceleration would double.
b. The acceleration would multiply by 4.
c. The acceleration would decrease by half.
d. The acceleration would not change.
____
9. Kathy goes for a jog. Two minutes later, Rachel also sets out for a jog.
The distance that they travel is plotted for 10 minutes.
What can you conclude about Kathy and Rachel's motion?
a. Kathy's speed increases at a constant rate for 10 minutes.
b. Rachel accelerates from 2 minutes to 7 minutes, then jogs at a constant speed.
c. Rachel jogs with an average speed of 120 meters/minute for her first 5 minutes.
d. If Kathy continues at the same pace, she will jog 2,400 meters in 20 minutes.
____ 10. Why must an air traffic controller know a plane's velocity?
a. to know how far away the plane is
b. to know how high the plane is flying
c. to know the plane's overall rate of motion
d. to know the plane's direction as well as its speed
____ 11. What does a horizontal slope for a distance-versus-time graph indicate about an object's motion?
a. The object moved faster.
b. The object did not move.
c. The object slowed down.
d. The object reversed direction.
____ 12. What is the difference between potential and kinetic energy?
a. Potential energy is energy due to motion. Kinetic energy is stored energy.
b. Potential energy is stored energy. Kinetic energy is energy due to motion.
c. Potential energy results from unbalanced forces. Kinetic energy results from
balanced forces.
d. Potential energy results when there is a net force. Kinetic energy results when
there is no net force.
____ 13. Which of the following is an application of Newton's Third Law of Motion?
a. A skydiver falls away from a plane toward the ground.
b. A truck accelerates more slowly when it is fully loaded than when it is empty.
c. A ball sits on the ground until a player kicks it. The nonzero net force sets the ball
in motion.
d. A rocket can accelerate when it pushes gas backward. The reaction force pushes
the rocket forward.
____ 14. If a bicyclist travels 30 kilometers in two hours, her average speed is
a. 30 km/h.
b. 60 km/h.
c. 15 km/h.
d. 2 km/h.
____ 15. A force is a push or pull that is described by its
a. direction.
b. speed and direction.
c. strength and direction.
d. strength.
____ 16. A student pushes a television cart to the left with a constant force of 100 N. The force of friction
between the cart and the floor pushes back to the right with a force of 75 N. If the cart was initially
at rest, how will it move as the constant force is applied?
a. At constant speed to the left
b. With constant acceleration to the left
c. With increasing acceleration to the left
d. To the left initially and then slow to a stop
____ 17. Unbalanced forces acting on an object will change the object's
a. mass.
b. height.
c. acceleration.
d. weight.
____ 18. A change in an object's motion is cause by
a. equal forces acting on that object.
b. unbalanced forces acting on that object.
c. balanced forces acting on that object.
d. None of the above
____ 19. Which of the following best describes average speed?
a. The speed of an object as it moves in a circular path.
b. The overall rate of speed at which an object moves.
c. The speed of an object at one instant of time.
d. The rate at which velocity remains constant.
____ 20. The arrows represent forces acting on four identical boxes. Which box experiences the greatest
unbalanced force?
a.
b.
c.
d.